Formulations containing a non-oxidative biocide and a source of active halogen and use thereof in water treatment

ABSTRACT

Novel formulations containing a non-oxidative biocide, such as DBNPA, and a source of an in situ produced active biocide, such as a concentrated aqueous solution of an inorganic halide salt, are disclosed. These novel formulations are particularly effective in the treatment of water, and are characterized by high stability, desirable rheological properties and an excellent biocidal activity.

BACKGROUND OF THE INVENTION

The present invention relates to the field of water purification and,more particularly, to novel formulations for water disinfestation,containing a combination of a non-oxidative biocide and a source of anoxidative biocide.

Biocidal treatment is an essential part of any water treatment, inparticular when treating industrial water, and is used to preventmicrobiological growth, biocorrosion and biofouling accumulation.Biocides are often classified according to their mode of operation, withthe most common classification being between oxidative and non-oxidativebiocides. Oxidative and non-oxidative biocides are commonly combined inorder to increase the biocidal efficiency of the treatment program.

Commonly used oxidative biocidal agents include active halogen-releasingcompound such as chlorine, bromine, hypochlorous acids and hypochloritesalts thereof, and hypobromous acids and hypobromite salts thereof, aswell as chlorine or bromine carriers such as halogenated hydantoins andhalogenated isocyanurates.

“Active halogen” is a phrase used herein to describe halogen compoundsor species in which the halogen atom has a +1 oxidation state (forexample CIO and BrO⁻), and is also known and referred to in the art as“free halogen” or “available halogen”. Active halogens are known ashighly effective antimicrobial agents, having a wide biocidal activity(e.g., antibacterial, antifungal, antialgae and antiviral activities),and thus are routinely used in water treatment systems.

Hypochlorous and hypobromous acids (HOCl and HOBr respectively) arecommon sources of active halogen and are frequently used as aggressiveoxidizing agents for various applications, including water treatmentsystems.

In water, the active halogen ion exists in equilibrium with thecorresponding acid, which in turn is in equilibrium with dissolvedhalogen gas (see, scheme 1 below), whereby the relative proportions ofthe active halogen and the corresponding acid are determined by pH andtemperature.

For example, in a chlorine based system, when the pH is between 2 and 7,the equilibrium is in favor of HOCl. As the pH falls below 2, thepredominant form of the chlorine is Cl₂. At a pH of 7.4, HOCl and OCl⁻are about equal, and as the pH goes above 7.4, increasing proportions ofOCl⁻ are present.

The hypochlorite and hypobromite ions are less effective oxidizingagents than the corresponding acids.

Chlorine based oxidants, such as hypochlorous acid, have severallimitations, as compared to bromine based oxidants. First, at a pHhigher than 7.5 (an industrially-common pH of, for example, coolingwater) the main species is the hypochlorite ion (OCl⁻), and not the moreactive biocidal species, hypochlorous acid (HOCl). Furthermore,hypochlorous acid reacts irreversibly with amines to producechloroamine, which is also less active as biocide.

Hypobromous acid is a more efficient biocide compared to hypochlorousacid for the following reasons: (i) at a pH of about 8-9, the amount ofnon-dissociated hypobromous acid is higher than that of non-dissociatedhypochlorous acid; (ii) the reaction of hypobromous acid with amines isreversible and thus, the presence of amines does not affect theefficiency of the biocide; and (iii) at the same pH and temperature, thevolatility of the hypobromous acid is lower than that of thehypochlorous acid, therefore loss by evaporation is reduced.

Hypobromous acid is obtained by reacting sodium bromide withchlorine-based oxidants. The hypobromous acid then reacts with thereactive species (inorganic, organic or microbes) and bromide (Br) isregenerated into the water.

Thus, commonly used water treatment systems often utilize sodium bromide(usually as a concentrated (e.g., 40%) aqueous solution thereof,otherwise known as “brine”) in combination with an oxidant such ashypochlorite, so as to generate the active hypobromous acid, as depictedin scheme 2 below:

As discussed hereinabove, non-oxidative biocidal agents are alsofrequency used in water purification systems. These include, forexample, aldehydes (e.g., formaldehyde, glutaraldehyde and acrolein),amine-type compounds (e.g., quaternary ammonium compounds), halogenatedcompounds (e.g., bronopol (2-bromo-2-nitro-1,3-propanediol)),terbutylazine (TRZ), 1,2-dibromo-2,4-dicyanobutane (DBDCB),2,2-dibromo-3-nitrilopropionamide (DBNPA)), sulfur-containing compounds(e.g., isothiazolone, thiocarbamates, thiocyanomethylbenzothiazole,copper sulfate and metronidazole), and quaternary phosphonium salts(e.g., tetrakis(hydroxymethyl)phosphonium sulfate (THPS)).

2,2-Dibromo-3-nitrilopropionamide, referred to hereinafterinterchangeably as DBNPA (presented in Scheme 3 below), is a broad rangenon-oxidative haloacetamide biocide, commonly used for disinfection ofcooling water and industrial water treatment. The solubility of DBNPA inwater, at ambient temperature, is only 1.7%. DBNPA is also highlyunstable in water, as it quickly degrades into ammonia and a bromideion. DBNPA is more stable under acidic aqueous conditions, typically ina pH range of 1 to 5 [see, for example, “Rates and Products ofDecomposition of 2,2-dibromo-3-nitrilopropionamide”, Exner et al., J.Agr. Food Chem., Vol. 21, No. 5, pp. 838-842, 1973].

Haloacetamides in general, and DBNPA in particular, can be utilized inwater treatment systems via various modes of applications.

The most common mode of application of DBNPA is as a liquid formulation.Since DBNPA has poor solubility in water, these formulations typicallycontain as a carrier a mixture of water and an organic solvent, mostoften a glycol (for example, polyethylene glycol (PEG), dipropyleneglycol (DPG) and others). Although the concentration of the DBNPA insuch liquid formulations may reach 50%, usually, it is reported as beingfrom 5% to 25%, with a concentration of glycol of at least 45% glycol.

The use of organic solvents, however, is generally undesirable due tocost ineffectiveness and environmental concerns, mainly due to anincrease of the organic loading of the treated water (chemical oxygendemand, COD) (see, for example, U.S. Pat. No. 5,627,135).

Liquid formulations of DBNPA, combining organic solvents and water, aredescribed, for example, in U.S. Pat. No. 4,163,796, which teachesaqueous antimicrobial compositions containing 2.5% DBNPA; in U.S. Pat.Nos. 4,163,797 and 4,232,041 and DE 2,854,078, which teach aqueousantimicrobial compositions containing 5% DBNPA; in U.S. Pat. No.4,163,795, which teaches aqueous antimicrobial compositions containing10% DBNPA; and in U.S. Pat. No. 3,689,660, which teaches stable liquidcompositions useful as antimicrobial agents, containing 15-25% DBNPA. InIL Patent No. 0065290, by the present assignee, aqueous antimicrobialcompositions containing 10% DBNPA are disclosed.

DBNPA sustained-release formulations are also common, containing variousadditives, such as polymeric matrices (for example, methyl cellulose),binders and compression agents in a significant amount. Exemplarysustained-release formulations are described in European Patent No.954966 and in WO 98/25458. Sustained-release formulations have similardrawbacks as the soluble liquid formulation, as such formulationscontain inert components that lead to an increase of the cost and theorganic loading. In addition, in most of these formulations the rate ofthe DBNPA dissolution is not constant, thus preventing optimal controlof the water body.

Alternatively, DBNPA is formulated as solid compacted products,available as granules or tablets (see, for example, European Patent No.1322600). This mode of application is direct and circumvents using asolvent. However, it requires a suitable feeding system which maycomplicate the application.

In order to overcome the disadvantageous features of the above-describedformulations, aqueous suspensions of DBNPA can be utilized. Suchsuspensions are typically obtained with the aid of suspending agents.Since DBNPA is stable in water only under acidic environment, specialsuspending agents, which are stable at a pH below 5, are required.Unfortunately, most of the commonly used suspending agents are eitherunstable or fail to exhibit the desired effect under acidic conditions.

For example, U.S. Pat. No. 5,627,135 teaches aqueous suspensions ofDBNPA having a pH in the range of 1 to 4 and containing xanthan gum as aproposed thixotropic suspending agent. The suspending agent is definedtherein as “a thixotrope that exhibits Ellis-Plastic behavior”, whichsuggests a high viscosity for avoiding sedimentation in a static state,and a moderate viscosity when pumping the slurry. The suspensions taughtin this patent comprise DBNPA at a concentration range of from 3% to 70%by weight in water.

Japanese patent No. 09295907 discloses a suspension of DBNPA in waterwith rhamsan gum as a suspending agent, and no reference to pH control.

U.S. Pat. No. 6,083,890 teaches that in DBNPA-containing compositionsstored for 7 days at ambient temperature and a pH of about 2.2 or less,xanthan gum loses a significant proportion, greater than 20%, of itsviscosifying functionality. Such a functionality loss evidently leads topoor product performance unless an increased concentration of xanthangum is initially used to compensate for the decrease in viscosity. Thus,the desirability of a low pH to preserve the haloacetamide conflictswith the adverse effects of a low pH on a suspending agent such asnatural xanthan gum.

U.S. patent application Ser. No. 10/052,115 having publication No.20020147235 discloses suspensions of haloacetamides in which a specialgroup of xanthan gums which contain no more than 1.2% acetic acid oracetate groups by weight, is utilized. This particular xanthan gum groupis more stable than the common xanthan gums.

Several reports teach using DBNPA in combination with othernon-oxidative biocides. For example, since DBNPA is active against sometypes of algae only at high concentrations, it has been utilized incombination with highly active anti-algae agents, such as terbutylazine(TBZ), mostly in aqueous suspensions, or 1,2-dibromo-2,4-dicyanobutane(dibromodicyanobutane, DBDCB) (see, for example, U.S. Pat. No.4,604,405).

As discussed hereinabove, oxidative and non-oxidative biocides arecommonly combined in order to increase the biocidal effect in watertreatment. Thus, several publications describe formulations that combinea non-oxidative agent such as DBNPA and an agent capable of forming anoxidizing agent, such as sodium bromide.

Thus, for example, liquid formulations containing 5% or 20% DBNPA, aswell as NaBr, HBr, hypobromous acid, water and tetraethylene glycol,which are used for disinfecting pulp and paper, and solid slow-releasedDBNPA solid tablets have been described (see,http:/www.amsainc.com/prod-dhnpa-overview.asp).

DBNPA liquid solutions in polyethylene glycol (PEG) 200 and/ortetraethyleneglycol and water (for example a 5% or 20% DBNPAformulation) are also disclosed (see, www.dowbiocides.com).

U.S. Pat. No. 3,928,575 discloses a solid composition of ahalocyanoacetamide, such as DBNPA, and at least 0.5 mole of awater-soluble bromide or iodide salt (such as sodium iodide), typicallybelow 10 moles, per moles of halocyanoacetamide, which was foundeffective in rapid destruction of microorganisms. This patent suggeststhat the antimicrobial activity of such a composition results frompotentiation of the halocyanoacetamide by the halide salt and that sucha potentiation results in synergism. The solid compositions taught inthis patent, however, typically includes from 1 to 10 weight percents ofthe halocyanoacetamide. No reference is made in this patent to acombination of DBNPA with an oxidative biocide, nor to an activation ofthe bromide or iodide salt, so as to produce an oxidative biocide.

Although these publications describe soluble liquid formulations orsolid formulations that contain combinations of DBNPA and bromides,these formulations suffer many disadvantages, such as limitedconcentration of DBNPA, high cost and non-friendly reagents, asdiscussed in detailed hereinabove. Currently known aqueous suspensionsof DBNPA also suffer disadvantages such as instability, limitedconcentration of DBNPA and/or insufficient efficacy.

Thus, there is a widely recognized need for, and it would be highlyadvantageous to have, novel, stable formulations that contain acombination of oxidative and non-oxidative reagents, which can bebeneficially used in water disinfestation, and are devoid of the abovelimitations.

SUMMARY OF THE INVENTION

The present invention provides novel formulations that comprise anon-oxidative biocide and an In situ produced active halogen source,preferably generated from an inorganic halide salt. These formulationswere found to be highly stable, as aqueous suspensions or as liquidformulations, even when high concentrations of the biocide are used.These formulations were further found highly effective in watertreatment, particularly in water disinfestation.

Thus, according to one aspect of the present invention there is provideda formulation comprising at least one non-oxidative biocide and aconcentrated aqueous solution of an inorganic halide salt, theformulation being in a form of a suspension According to furtherfeatures in preferred embodiments of the invention described below, thehalide salt produces an active halogen upon activation by an oxidizer.

According to still further features in the described preferredembodiments the oxidizer is selected from the group consisting ofchlorine, bromine, hypochlorite salt, hypochlorous acid, hypobromitesalt, hypobromous acid a halogenated hydantoin, a halogenatedisocyanurate, a peroxide and a persulfate.

According to another aspect of the present invention there is provided aformulation comprising at least one non-oxidative biocide, a source ofan in slit produced active halogen and an aqueous solvent, theformulation being in a form of a suspension.

According to further features in preferred embodiments of the inventiondescribed below, the active halogen is produced in situ upon activationby an oxidizer.

According to still further features in the described preferredembodiments the source of the active halogen is a concentrated aqueoussolution of an inorganic halide salt.

According to yet another aspect of the present invention there isprovided a formulation comprising 2,2-dibromo-3-nitrilopropionamide(DBNPA) and sodium bromide brine, the formulation being in a form of asuspension.

According to further features in preferred embodiments of the inventiondescribed below, the sodium bromide produces an active halogen uponactivation by an oxidizer.

According to still further features in the described preferredembodiments the formulation further comprises at least one additionalbiocide.

According to still further features in the described preferredembodiments an amount of the DBNPA and the sodium bromide is greaterthan 30 weight percents of the total weight of the formulation.

According to still further features in the described preferredembodiments an amount of the DBNPA ranges from 3 weight percents and 70weight percents of the total weight of the formulation. Preferably, theamount of the DBNPA is greater than 20 weight percents of the totalweight of the formulation.

According to still further features in the described preferredembodiments the DBNPA and the sodium bromide and/or active halogenformed thereby act in synergy.

According to still further features in the described preferredembodiments the formulation described herein is characterized by a shearrate higher than 300 Pa at a speed smaller than 100 rpm.

According to still further features in the described preferredembodiments the formulation described herein is characterized by a shearrate lower than 300 Pa at a speed equal to or higher than 100 rpm.

According to still further features in the described preferredembodiments an average particle size of the non-oxidative biocide or theDBNPA in the suspension is less than 200 microns.

According to still further features in the described preferredembodiments there is provided the formulation described herein, furthercomprising a suspending agent. Preferably, an amount of the suspendingagent is lower than 2 weight percents of the total weight of theformulation. Yet preferably, the suspending agent is a water-solublesuspending agent.

According to still further features in the described preferredembodiments there is provided the formulation described herein, furthercomprising a foaming agent.

According to still another aspect of the present invention there isprovided a liquid formulation comprising at least one non-oxidativebiocide, a concentrated aqueous solution of an inorganic halide salt,and a polyethylene glycol having an average molecular weight higher than100 grams/mol.

According to further features in preferred embodiments of the inventiondescribed below, an amount of the polyalkylene glyocol is lower than 50weight percents of the total weight of the formulation.

According to still further features in the described preferredembodiments, the amount of the non-oxidative biocide and the halide saltis greater than 70 weight percents of the total weight of theformulation.

According to still further features in the described preferredembodiments there is provided the formulation described herein, whereinan amount of the non-oxidative biocide ranges from about 3 weightpercents to about 70 weight percents of the total weight of theformulation.

According to still further features in the described preferredembodiments the amount of the non-oxidative biocide is greater than 50weight percents of the total weight of the formulation.

According to still further features in the described preferredembodiments the at least one non-oxidative biocide is selected from thegroup consisting of an aldehyde-based non-oxidative biocide, anamine-containing non-oxidative biocide, an amide-containingnon-oxidative biocide, an imide-containing non-oxidative biocide, ahalogenated non-oxidative biocide, a sulfur-containing non-oxidativebiocide, a quaternary phosphonium-containing non-oxidative biocide, anammonium salt-containing non-oxidative biocide and any combinationthereof. Preferably, the halogenated non-oxidative biocide is selectedfrom the group consisting of bronopol, terbutylazine,1,2-dibromo-2,4-dicyanobutane, 2-bromo-2-cyano-acetamide,2,2-dibromo-2-cyanoacetamide, 2-bromo-2-chloro-2-cyanoacetamide and2,2-dibromo-3-nitrilopropionamide.

According to still further features in the described preferredembodiments the at least one non-oxidative biocide comprises2,2-dibromo-3-nitrilopropionamide (DBNPA).

According to still further features in the described preferredembodiments the concentrated aqueous solution of the inorganic halidesalt is a saturated solution of the halide salt.

According to still further features in the described preferredembodiments the inorganic halide salt is selected from the groupconsisting of an inorganic bromide salt and an inorganic chloride salt.

According to still further features in the described preferredembodiments the inorganic halide salt is an inorganic bromide salt.Preferably, the inorganic bromide salt is selected from the groupconsisting of sodium bromide, magnesium bromide, calcium bromide,lithium bromide, ammonium bromide and potassium bromide.

According to still further features in the described preferredembodiments, in each of the formulations described herein, the at leastone non-oxidative biocide and the inorganic halide salt and/or activehalogen formed thereby act in synergy.

According to still further features in the described preferredembodiments each of the formulations described herein is stable for atleast 1 week upon storage at ambient temperature. Preferably, theformulation is stable for at least 10 days upon storage at ambienttemperature.

According to still further features in the described preferredembodiments each of the formulations described herein is stable for atleast 1 week upon storage at 50° C.

According to still further features in the described preferredembodiments the formulations described herein are identified for use inwater disinfection.

According to an additional aspect of the present invention there isprovided a method of water disinfestation, the method comprisingcontacting the water with at least one non-oxidative biocide and an insitu-produced active halogen.

According to further features in preferred embodiments of the inventiondescribed below, the active halogen is obtained by an in situ activationof an inorganic halide salt by an oxidizer.

According to still further features in the described preferredembodiments the at least one non-oxidative biocide is2,2-dibromo-3-nitrilopropionamide (DBNPA).

According to yet an additional aspect of the present invention there isprovided a method of water disinfestation, the method comprisingcontacting the water with any of the formulations as described herein.

According to further features in preferred embodiments of the inventiondescribed below, the contacting is performed intermittently.

According to still further features in preferred embodiments of theinvention described below, the contacting is performed continuously.

According to still further features in the described preferredembodiments the method further comprising contacting the water with anoxidizer.

The present invention successfully addresses the shortcomings of thepresently known configurations by providing novel formulations, whichexhibit exceptional stability, biocidal efficacy and rheologicalbehavior, and are thus far superior to known biocidal formulations.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. In case of conflict, the patentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

As used herein, the term “comprising” means that other steps andingredients that do not affect the final result can be added. This termencompasses the terms “consisting of” and “consisting essentially of”.

The phrase “consisting essentially of” means that the composition ormethod may include additional ingredients and/or steps, but only if theadditional ingredients and/or steps do not materially alter the basicand novel characteristics of the claimed composition or method.

The term “method” or “process” refers to manners, means, techniques andprocedures for accomplishing a given task including, but not limited to,those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical, pharmacological, biological,biochemical and medical arts.

As used herein, the singular form “a,” “an,” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

Throughout this disclosure, various aspects of this invention can bepresented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc, as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings. With specific reference now tothe drawings in detail, it is stressed that the particulars shown are byway of example and for purposes of illustrative discussion of thepreferred embodiments of the present invention only, and are presentedin the cause of providing what is believed to be the most useful andreadily understood description of the principles and conceptual aspectsof the invention. In this regard, no attempt is made to show structuraldetails of the invention in more detail than is necessary for afundamental understanding of the invention the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the invention may be embodied in practice. In the drawings:

FIG. 1 presents comparative plots demonstrating the synergistic effectof a DBNPA/NaBr aqueous suspension containing 58 weight percents DBNPA,upon incubation with bacterial beads in the presence of sodiumhypochlorite.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of novel formulations containing a combinationof a non-oxidative biocide and an in situ produced active halogen as anoxidative biocide, which can be advantageously utilized for waterdisinfestation. Specifically, the present invention is of aqueoussuspensions of a non-oxidative biocide and a source of an in situproduced oxidative biocide, preferably being a concentrated aqueoussolution of an inorganic halide salt, which are highly stable, andexhibit desirable rheological properties, when a high concentration ofthe biocide is utilized, and further exhibit a high biocidal activity.The present invention is further of liquid formulations containing anon-oxidative biocide and a source of an in situ produced oxidativebiocide, preferably being an inorganic halide salt and an organicsolvent. The present invention is further of processes of preparingthese formulations and of methods utilizing same, preferably incombination with an oxidizer, for treating contaminated water.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments or of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

As discussed in detail hereinabove, biocidal treatment of water (alsoknown as water disinfestation) involves oxidative and non-oxidativebiocides.

Active halogens are known as highly effective oxidative antimicrobialagents, having a wide biocidal activity, and are indeed frequently usedin water treatment systems. Among active halogens, bromine-basedoxidative biocides are considered superior to chlorine-based oxidativebiocides for many industrial water treatment applications. Activebromines are obtained, for example, by reacting sodium bromide, eithersolid or in aqueous/brine solutions, with chlorine-based oxidants.

Amongst the commonly used non-oxidative biocides, halogenated compounds,such as bronopol, terbutylazine (TBZ). 1,2-dibromo-2,4-dicyanobutane(dibromodicyanobutane, DBDCB) and 2-2-dibromo-3-nitrilopropionamide(DBNPA), constitute an important group.

As further discussed in detail hereinabove, DBNPA is a common andeffective non-oxidative biocide, often used in industrial watertreatment. Most of the currently known formulations of DBNPA includeliquid formulations, sustained-release formulations and solidcompositions. However, these formulations suffer several disadvantages,as follows:

(a) the low solubility and instability of DBNPA in water oftennecessitates using organic solvents, such as polyethylene glycols, invery high concentrations (up to about 60%), a feature which isenvironmentally and economically undesirable, and increases the organicloading of the treated water;

(b) the concentration of the DBNPA in these liquid formulations isusually low, between 5% to 25%;

(c) DBNPA sustained-release formulations have similar drawbacks as thesoluble liquid formulation, and in addition, the DBNPA dissolution isnot constant and controlling the water treatment process is difficult;and

(d) using solid compacted DBNPA requires a suitable feeding system whichmay complicate its application.

Due to the environmental and economical deficiencies of liquidformulations and limited applications of solid compositions, aqueoussuspensions of DBNPA and other non-oxidative biocides is an attractiveform for formulating such agents. Such a formulation form is produced atmuch lower cost, compared to liquid formulations, and results in a muchlower environmental impact (due to a decreased Carbon Oxygen Demand(COD)), while avoiding the risk of solvent-based products actuallyencouraging biogrowth. Further, aqueous suspension forms are favorablein comparison to solid formulations, since they are more easilycontrolled, and do not require a particularly suitable feeding system.

However, as discussed hereinabove, aqueous suspensions of DBNPA requirethe use of suspending agents, whereby most commonly-used suspendingagents are unstable under acidic conditions, in which the DBNPA isstable.

Furthermore, when intended for an industrial application, aqueoussuspensions should exhibit certain properties, in order to allow anefficient utilization thereof. Such an industrial suspension has to bepseudo-plastic, namely, to show a high viscosity at low shear rate, soas to avoid settling of the solid; and to show a low viscosity at highershear rate, so as to permit flow and pumping of the suspension. Therheological behavior of the suspension is dependant on the solidparticles' size, the charge distribution on the solid's surface and onthe pH, the ionic strength and the viscosity of the suspending phase.

Some aqueous suspensions of DBNPA are disclosed in the art, yet, mostare unsuitable for the industrial water treatment applications, due tothe conflict of DBNPA stability and suspending agent stability at highpH values

In a search for formulations that could be utilized in an efficacious,cost-effective and environmental-friendly method of treating water, thepresent inventors have now surprisingly found that non-oxidativebiocides such as DBNPA can be successfully formulated with aconcentrated aqueous solution of an inorganic halide salt such as sodiumbromide brine. Inorganic halide salts can serve as a source of an activehalogen (formed upon contacting the halide salt with an oxidizer) andhence, such formulations combine oxidative and non-oxidative biocides.The present inventors have further surprisingly found that theseformulations can be formed as highly stable aqueous suspensions that arecharacterized by the desired rheological properties and by the desiredbiocidal activity for the disinfection of water.

As demonstrated in the Examples section that follows, organicsolvent-free, aqueous suspension formulations, containing highconcentrations of DBNPA in combination with various halide brines, wereprepared, and exhibited a high stability, desirable viscosity and highbiocidal efficacy. For example, a 55% milled DBNPA aqueous suspension,containing a solution of 40% NaBr brine, was tested in a field test andwas demonstrated to reduce the bacterial count in a cooling water towerfrom above 10⁵ CFU/ml to lower than 10³ CFU/ml (see, Example 22), withina few days (CFU=Colony Forming Units).

Thus, according to one aspect of the invention there is provided aformulation which comprises one or more non-oxidative biocides and aconcentrated aqueous solution of an inorganic halide salt, theformulation being in a form of a suspension.

As used herein and is well known in the art, the term “suspension”describes an intimate mixture of two substances: the suspended(dispersed) phase (suspenoid), which includes a substance in a finelydivided state, which is uniformly distributed through the secondsubstance, called the suspending phase (or dispersing medium).

The suspending phase may be a gas, a liquid, or a solid and thesuspended phase may also be any of these, with the exception of one gasin another. A suspension typically separates itself by gravitationalaction into two visibly distinct portions over time. Such a phenomenonis also commonly referred to as settling out and a stability of asuspension is typically defined by the time period required for thesettling out to be effected.

An “aqueous suspension” is therefore a suspension as defined herein inwhich the suspended phase includes solid particles and the suspendingphase is an aqueous solution.

As used herein, the term “biocide” describes an agent that is capable ofdestroying or killing an organism, or of materially inhibiting thegrowth of an organism.

The term “organism” is used herein to describe organisms which aretypically pathogenic to humans or animals during one or more of theirlife cycles, or disrupt the local ecology. This term further encompassesorganisms, which, although not pathogenic or ecologically disruptive,are typically destructive of industrial processes or equipment.

Examples include fungi and their spores, protozoans and their cysts,bacteria and their spores, algae, viruses, helminthes or their ova,insects, small fish and their ova, mollusks and their ova, and othertypes of living organisms. The organisms may be micro-cellular,uni-cellular, multi-cellular, and the like. Preferably, the biocidesutilized in the context of the present invention are suitable for useagainst organisms, in particular microorganisms, that typically grow inwatery environments. These include, for example, bacteria, viruses,coliforms, fungi and algaes.

The term “non-oxidative biocide”, also referred to hereininterchangeably as “non-oxidative agent”, “non-oxidizing agent” and“non-oxidizing biocide”, refers to a biocide which, while during thedisinfestation (interfering with the life cycle of an organism) process,does not undergo a change in its oxidation state.

Preferred non-oxidative biocides, according to the present embodimentsinclude, but are not limited to, aldehyde-based non-oxidative biocides,amine-based non-oxidative biocides, amide-based non-oxidative biocidesand imide-based non-oxidative biocides, halogenated non-oxidativebiocides, sulfur-containing non-oxidative biocides, quaternaryphosphonium salt-containing non-oxidative biocides, ammoniumsalt-containing non-oxidative biocides and any combination thereof.

Aldehyde containing biocides may be linear, branched or aromatic.Examples of aldehyde-based biocide include, but are not limited to,formaldehyde, glutaraldehyde and acrolein.

Examples of halogenated biocides include, but are not limited to,bronopol, terbutylazine (TBZ), and halocyanoacetamides such as1,2-dibromo-2,4-dicyanobutane (dibromodicyanobutane DBDCB),2-bromo-2-cyano-acetamide, 2,2-dibromo-2-cyanoacetamide,2-bromo-2-chloro-2-cyanoacetamide and 2-2-dibromo-3-nitrilopropionamide(DBNPA).

Exemplary sulfur-containing non-oxidative biocides include, but are notlimited to, isothiazolone, thiocarbamates, thiocyanomethylbenzothiazole,copper sulfate and metronidazole.

Exemplary quaternary phosphonium salt-containing non-oxidative biocidesinclude, but are not limited to, tetrakis(hydroxymethyl)phosphoniumsulfate (THP).

Preferably, the non-oxidative biocide is a halogenated non-oxidativebiocide and more preferably it is a halocyanoacetamide, as detailedhereinabove and further as described, for example, in U.S. Pat. No.3,928,575, which is incorporated by reference as if fully set forthherein.

According to the presently most preferred embodiments of the presentinvention, the non-oxidative biocide is DBNPA. DBNPA can be utilized asa single non-oxidative biocide or in combination with one or moreadditional non-oxidative biocides, as described herein.

The non-oxidative biocide(s) utilized in each of the formulationsdescribed herein can be selected upon the desired application of theformulation, namely; the most suitable agent for killing a targetmicroorganism can be utilized.

The term “inorganic halide salt” refers to a salt of an inorganicelement or moiety and one or more halides, whereby the number of halidesdepends on the valency of the inorganic element or moiety.

The term “halide” describes an anion of a halogen and can be fluoride,chloride, bromide or iodide. Preferably, the inorganic halide salt is aninorganic bromide salt, an inorganic chloride salt or a combinationthereof

As detailed in the background hereinabove, bromine-based oxidativeagents are considered highly suitable for the treatment of industrialwater, since at high pH levels, associated with industrial water, thehypobromous acid is a highly efficient biocide, is less affected by thepresence of amines, and has a low volatility. Thus, according topreferred embodiments of the present invention, the inorganic halidesalt is an inorganic bromide salt.

Exemplary inorganic bromide salts include, but are not limited to,sodium bromide, magnesium bromide, calcium bromide, lithium bromide,ammonium bromide and potassium bromide. According to the presently mostpreferred embodiment of the present invention, the inorganic halide saltis sodium bromide.

Thus, further according to the presently most preferred embodimentsdescribed herein, an aqueous suspension formulation, according to thisaspect of the present invention, comprises DBNPA and a concentratedsolution of sodium bromide.

As used herein, the phrase “concentrated aqueous solution” with respectto inorganic halide salt describes an aqueous solution in which theconcentration of the halide salt is preferably higher than 5 weightpercents, more preferably higher than 20 weight percents, and morepreferably higher than 30 weight percents, and can be, for example 10weight percents, 20 weight percents, 30 weight percents, 40 weightpercents, and even 50 weight percents and 60 weight percents and higher,including any numeral from 10 to 60 and higher, depending on thesaturation level of a particular salt.

Preferably, the concentrated inorganic halide salt is a saturated, oralmost saturated, aqueous solution of the salt, also known and referredto herein as brine. Without being bound to any particular theory, it issuggested that the brine solution has a stabilizing yet dispersingeffect on the formulation, and contributes to the high stability of theprepared suspensions, and to the desirable rheological propertiesthereof.

As can be seen in comparative experiments shown below (see for example,Examples 11 and 14), when water was used instead of brine, a moreviscous suspension was obtained, rendering it difficult to pour andun-pumpable by a peristaltic pump.

A brine is achieved at different concentrations for different salts,depending on various aspects, such as the solubility of the salt, thetemperature, the pH etc.

Typically, as is known in the art, when a mixture of a substance, andparticularly a substance that has poor solubility in aqueous solutions,and a saturated aqueous solution of a salt is formed, an effect ofsalting out is observed, namely, the substance is separated from theaqueous solution and no uniform suspension is obtained. In the case ofthe present embodiments, stable and uniform suspensions of non-oxidativebiocides are obtained and no salting out effect is observed.

As detailed in the background section hereinabove, halides may reactwith oxidizing agents to produce active halogens as strong oxidizingagents (oxidative biocides).

Thus, according to a preferred embodiment of the present invention, thehalide salt is capable of producing an active halogen, as definedhereinabove, upon activation by an oxidizer.

Since, as explained in detail hereinabove, the hypobromous acid is ahighly efficient biocide, preferably, the active halogen is activebromine.

As shown in scheme 2 hereinabove, a halide, such as bromide, can reactwith an oxidant such as hypochlorite, so as to generate the activehypobromous acid. This hypobromous acid generates an active brominewithin the aquatic environment, which acts as an active oxidativebiocide.

As used herein, the term “oxidizer” describes a substance that induces achange in an oxidizing state of another substance, by way of elevatingthe oxidizing state (reducing the number of electrons) of the othersubstance.

Preferably, the oxidizer may be any one or more of known oxidativebiocides, such as, but not limited to a halogen oxidizer, a halogencarrier and a non halogen oxidizer.

Examples of halogen oxidizers include, but are not limited to chlorine,bromine, hypochlorite salts, hypochlorous acid, hypobromite salts andhypobromous acid.

Examples of halogen carriers, such as chlorine or bromine carriers,include, but are not limited to, halogenated hydantoins and halogenatedisocyanurates.

Examples of non halogen oxidizers include but are not limited to,peroxides (such as hydrogen peroxide) and per sulfates (such as oxone).

According to a preferred embodiment of the present invention, the activehalogen is prepared in situ, as defined hereinbelow, upon contacting theformulation described herein with an oxidizer, as described herein.

Further preferably, the combined system of a non-oxidative biocide, suchas DBNPA, and an active halogen produced from a concentrated aqueoussolution of a halide salt, act in synergy. As demonstrated in theExamples section that follows, it has been shown that the biocidalactivity of a DBNPA/NaBr aqueous suspension, in the presence of anoxidizer, is higher than that of DBNPA and NaBr, when each is usedalone, and is further higher that the sum of the activities exerted byeach of these agents alone. Moreover, a synergistic biocidal activitywas demonstrated when a system of microbial beads, simulating of abiofilm, was used. Treatment of such a system is very difficult andhence demonstration of a synergistic effect in such a system isparticularly indicative.

Without being bound to any particular theory, it is suggested thatutilizing the combined formulation of an oxidative and non-oxidativebiocides presented herein involves a halide generating cycle, in which,in addition to the initial halide salt within the formulation,additional halide is continuously generated as a result of both DBNPAdecomposition and hypobromous acid reaction.

Thus, according to another aspect of the present invention, there isprovided a formulation which comprises at least one non-oxidativebiocide, as described herein, a source of an in situ produced activehalogen and an aqueous solvent. Such a formulation is preferably beingin a form of a suspension.

As used herein, the phrase “a source of an in situ produced activehalogen” describes a substance that is capable of producing an activehalogen in situ, namely, via a reaction that occurs between an agentwithin the formulation and an agent in the treated medium (as opposed toan addition of an active halogen from an external source to theformulation). Preferably, such a substance reacts with an oxidizer thatis contacted with the formulation, to thereby produce the activehalogen. The in situ formed active halogen, serving as an oxidativebiocide, acts together with the non-oxidative biocide, preferably insynergy, as detailed hereinabove.

Each of the formulations described herein are desirably characterize ascapable of comprising the non-oxidative biocide and the halide salt, asdescribed herein, in relatively large amounts, which provide forenhanced biocidal activity exerted thereby.

Thus, in preferred embodiments, an amount of a non-oxidative biocidetogether with an inorganic halide salt is greater than 30 weightpercents of the total weight of the formulation, preferably greater than50 weight percents and can therefore be, for example, 32 weightpercents, 33 weight percents, 34 weight percents, 35 weight percents, 36weight percents, 37 weight percents, 38 weight percents, 39 weightpercents, 40 weight percents, 41 weight percents, 42 weight percents, 43weight percents, 44 weight percents, 45 weight percents, 46 weightpercents, 47 weight percents, 48 weight percents, 49 weight percents, 53weight percents and even higher, for example, 51 weight percents, 52weight percents, 53 weight percents, 54 weight percents, 55 weightpercents, 56 weight percents, 57 weight percents, 58 weight percents, 59weight percents, 60 weight percents, 60 weight percents, 61 weightpercents, 61 weight percents, 63 weight percents, 64 weight percents, 65weight percents, 66 weight percents, 67 weight percents, 68 weightpercents, 69 weight percents, 70 weight percents, and up to 80 weightpercents of the total weight of the formulation.

Further according to preferred embodiments of this aspect of the presentinvention, the formulation described herein contains a non-oxidativebiocide in an amount that ranges from 3 weight percents to 70 weightpercents, and preferably in an amount higher than 20 weight percents ofthe total weight of the formulation, and hence in an amount of, forexample, 21 weight percents, 22 weight percents, 23 weight percents, 24weight percents, 25 weight percents, 26 weight percents, 27 weightpercents, 28 weight percents, 29 weight percents, 30 weight percents, 31weight percents, 32 weight percents, 33 weight percents, 34 weightpercents, 35 weight percents, 36 weight percents, 37 weight percents, 38weight percents, 39 weight percents, 40 weight percents, 41 weightpercents, 42 weight percents, 43 weight percents, 44 weight percents, 45weight percents, 46 weight percents, 47 weight percents, 48 weightpercents, 49 weight percents, 50 weight percents, 51 weight percents, 52weight percents, 53 weight percents, 54 weight percents, 55 weightpercents, 56 weight percents, 57 weight percents, 58 weight percents, 59weight percents, 60 weight percents, and even higher, up to 65 weightpercents, 66 weight percents, 67 weight percents, 68 weight percents, 69weight percents, and even 70 weight percents of the total weight of theformulation.

While, as discussed hereinabove, currently available formulations ofnon-oxidative agents such as DBNPA are limited to relatively lowconcentrations of the biocide, it has now been found that stableformulations, containing much higher concentration of the biocide can beobtained.

As discussed hereinabove, the aqueous suspension formulations describedherein, in addition to exhibiting an exceptional biocidal activity, aresurprisingly and desirably characterized by other properties such ashigh stability and suitable viscosity.

As demonstrated in the Examples section that follows, these formulationswere stable for prolonged time periods, reaching several weeks.

Thus, according to a preferred embodiment of the present invention, theaqueous suspension formulations described herein are stable for a timeperiod of at least 7 days, preferably at least 10 days, when kept atambient temperature (see, Examples 1,2, 7, 8, 9, 12, 15 and 16).

The term “ambient temperature” refers to room temperature conditions,ala is generally a temperature between about 18° C. and about 35° C.

Further, the aqueous suspension formulations described herein arepreferably stable for a time period of at least 7 days when kept at 50°C. (see, Example 2).

As further discussed hereinabove, industrial suspensions are required toshow a high viscosity at low shear rate, so as to avoid settling of thesolid; and to show a low viscosity at higher shear rate, so as to permitflow and pumping of the suspension.

As demonstrated in Table 1 in the Examples section that follows, theaqueous suspension formulations presented herein exhibited high shearrates at low speeds (for example, 3 or 6 rpm), while exhibiting lowshear rates at higher speeds (10, 200, 300 and 600 rpm).

According to preferred embodiments of this aspect of the presentinvention, the aqueous suspensions described herein are thereforeadvantageously characterized by such a viscosity, that at low speeds,namely at a speed smaller than 100 rpm, the shear rate is higher than300 Pascals (Pa). According to some of the presently most preferredembodiments, at such speeds, the shear rate is higher than 700 Pa,higher than 1200 Pa and even higher than 2000 Pa.

According to preferred embodiments of this aspect of the presentinvention, the aqueous suspensions described herein are alsoadvantageously characterized by such a viscosity, that at high speeds,namely at speeds equal to or higher than 300 rpm, the shear rate islower than 300 Pa. According to some of the presently most preferredembodiments, at such speeds, the shear rate is lower than 100 Pa andeven lower than 50 Pa.

The rheological behavior of suspensions is typically dependant, iteralia, on the solid particles' size.

Thus, according to a preferred embodiment of the present invention, theaverage particle size of the non-oxidative biocide is less than 200microns. Preferably, the average particle size of the non-oxidativebiocide is less than 100 microns, more preferably less than 50 microns,and more preferably less than 20 microns. For example, DBNPA suspensionshave been prepared, wherein the average particle size of the DBNPA was57 microns (Example 14), 20 microns (Example 11) and 29 microns (Example10). These suspensions exhibited excellent stability and goodrheological properties.

The particle size may further be characterized, in addition or in placeof the average particle size, by the d50 or d98 values thereof, meaningthe size under which 50% of the particles reside (d50), or the sizeunder which 98% of the particles reside.

Thus, according to a preferred embodiment of the present invention, thed50 of the non-oxidative biocide particles size is less than 50 microns,preferably less than 10 microns. Yet according to another preferredembodiment of the present invention, the d98 of the non-oxidativebiocide particles size is less than 100 microns, preferably less than 50microns.

The aqueous suspension formulations described herein may furthercomprise a suspending agent. Preferably, the suspending agent is awater-soluble suspending agent. Exemplary suspending agent include, butare not limited to, xanthan gum, sodium carboxymethylcellulose,polyacrylic acid, tragacanth, polymethyl vinyl ether/maleric anhydridecopolymer, polyethylene oxide, methylcellulose, karya gum,methylethylcellulose, soluble starch, geletan, pectin, polyvinylalcohol, polyhydroxymethacrylate, hydroxypropyl cellulose, carbomers,chitin, gum acacia, and mixtures thereof.

Foaming agents may also be used to stabilize the suspension in a form of“foam”, as shown, for example, in Example 1 hereinbelow. Arepresentative example of a suitable foaming agent is linear alkylbenzene sulfonic acid (LABS).

The amount of the suspending agent and/or foaming agent can range fromof weight percent to 5 weight percents of the total weight of theformulation.

As shown, however, in the Examples section that follows, due to thestability of the suspensions, relatively low amount of these agents canbe utilized. Thus, preferably, the amount of the suspending agent and/orfoaming agent is lower than 2 weight percents, and more preferablyranges from 0.3 weight percent to 1.1 weight percents of the totalweight of the formulation.

As demonstrated in the Examples section that follows, treating a coolingwater tower with a combination of sodium hypochlorite (10%) oxidizer anda 55% milled DBNPA formulations, containing a NaBr 40% brine, resultedin a substantial reduction of the microbial count from more than 10⁵CFU/ml to less than 10³ CFU/ml, indicating a high biocidal activity.Thus, any of the formulations described herein may be used in waterdisinfection, and may suitably be identified as such.

The aqueous suspension formulations described herein are thus highlysuitable to disinfect water, having the following advantages:

-   -   the formulations are effective biocides;    -   the formulations are solvent-free, which is an environmental,        economical and biocidal advantage, as detailed hereinabove;    -   the aqueous suspension formulations are both stable and        pourable, thus suitable for the treatment of water bodies;    -   the formulations are easy to control and add to water systems,        being aqueous suspensions and not solid formulations;    -   the formulations can contain high concentrations of biocides,        and are thus suitable to use in the treatment of heavily        polluted or infected water systems with significant logistics        and handling advantages;    -   the formulations exhibit a synergistic effect by the combination        of both a non-oxidative biocide and a concentrated aqueous        halide salt, which keeps generating fresh halides in situ, in        the presence of common oxidizers.

As further demonstrated in the Examples section that follows, whilemaintaining the methodology of using a combination of a non-oxidativebiocide and a substance that can act as a source of an in situ producedactive halogen, the present inventors have successfully practiced liquidformulations that comprise such a combination. More specifically, thepresent inventors have prepared stable liquid formulations of anon-oxidative biocide such as DBNPA, in a relatively high concentration,and inorganic halide salts, which further include an organic solvent, ina relatively low amount. By using a high concentration of thenon-oxidative biocide, lower amounts of the formulation are requiredduring a water treatment process, thus circumventing the limitationsassociated with excessive amounts of organic solvents. Obviously, byusing lower amounts of an organic solvent, the limitations associatedwith excessive amounts of organic solvents are also circumvented.

As described in detail in the background hereinabove, presently knownnon-oxidative biocidal liquid formulations, such as DBNPA liquidformulations contain at least 45% by weight of a glycol, such as PEG, inorder to achieve stability, and the amount of DBNPA rarely exceeded 25%(see, for example, U.S. Pat. Nos. 3,689,660, 4,163,796, 4,163,797,4,163,795 and 4,232,041 and DE 2,854,078, supra).

Thus, according to another aspect of the present invention there isprovided a liquid formulation which comprises at least one non-oxidativebiocide, as described herein, a concentrated aqueous solution of aninorganic halide salt, as described herein, and a polyalkylene glycol.Preferably, the polyalkyleneglycol has a molecular weight higher than100 Daltons (Da), more preferably higher than 200 Da, as detailedhereinbelow.

Further preferably, the amount of the non-oxidative biocide in such aformulation is 20 weight percents of the total weight of theformulation, and more preferably is higher than 20 weight percents ofthe total weight of the formulation, and can be, for example, 25 weightpercents, 30 weight percents, 35 weight percents, 40 weight percents, 45weight percents, 50 weight percents, 55 weight percents 60 weightpercents and even higher, including any other numeral between 20 and 70weight percents of the total weight of the formulation

As used herein the term “polyalkylene glycol”, encompasses liquid andsolid polymers of the general formula HO—[(CH₂)m-O-]nCH₂OH, where m isan integer from 2 to 6 and n is greater than or equal to 4.

Preferably the polyalkylene glycol is a polyethylene glycol, alsoreferred to herein as its abbreviation PEG.

Exemplary polyethylene glycols that are suitable for use in this contextof the present invention include, but are not limited to, polyethyleneglycols having a molecular weight greater in the range of 100 to 2,000(Da) such as PEG 100, having an average molecular weight of about 100Da, PEG 200, having an average molecular weight of about 200 Da, PEG300, having an average molecular weight of about 300 Da, PEG 400, havingan average molecular weight of about 400 Da, PEG 600, having an averagemolecular weight of about 600 Da, PEG 1000, having an average molecularweight of about 1000 Da, and up to PEG 2000, having an average molecularweight of about 2000 Da. Preferably, the polyethylene glycol has anaverage molecular weight in the range of from 200 Da to 400 Da.

Surprisingly, it has now been found that a lower amount of PEG can beused while maintaining the stability of the formulation. For example, ithas been found that a liquid formulation containing 20 weight percentsDBNPA, 32 weight percents PEG 400, water and NaBr, is stable (see,Example 4 hereinbelow), while the same formulation excluding the sodiumbromide resulted in a precipitation of solid DBNPA at the bottom of theflask (see Example 5 hereinbelow).

Thus, in preferred embodiments, an amount of the polyethylene glycol islower than 50 weight percents of the total weight of the formulation,preferably lower than 45 weight percents, more preferably lower than 40weight percents, more preferably lower than 35 weight percents, and morepreferably lower than 30 weight percents.

Further according to preferred embodiments, the concentration of theinorganic halide salt (e.g., sodium bromide) utilized in suchformulations ranges from 10 weight percents to 40 weight percents.

Preferably, the formulations according to these embodiments of thepresent invention do not include hypobromous acid or any other oxidizingagent. Further preferably, these formulations are devoid of HBr.

As discussed hereinabove, the present inventors have shown that highlyactive biocidal formulations, in various forms, are obtained byutilizing a non-oxidative biocide and a substance that can produce anactive halogen in situ (e.g., an inorganic halide salt), as definedherein.

Thus, according to another aspect of the invention, there is provided amethod of water disinfestation, which is effected by contacting thewater with at least one non-oxidative biocide and an in situ producedactive halogen.

The contacting may be performed intermittently or continuously.

The method may further be effected by contacting the water with anoxidizer, as detailed hereinabove.

Further according to the present invention there is provided a method oftreating water, which is effected by contacting the water with any ofthe formulations described herein.

In a typical process, the water source is treated by a continuous orbatch wise addition of an oxidizer (e.g., 10% sodium hypochloritesolution), which is replaced occasionally by a formulation containing anon-oxidative biocide, according to the present embodiments, wherebyreplacing the two treatment solutions by one another can be performedrepetitively. Thus, water is treated by an oxidizer solution, then by anon-oxidative biocide formulation, then by an oxidizer solution, and soon. The time interval between switching the treatment solution and thetime during which each treatment solution is applied are determinedaccording to the treated system.

The formulations and methods described herein can be used in many watertreatment applications. Exemplary applications include treatment ofdrinking later, sewage water, process water systems, such as inpapermaking or in industrial cooling water systems, washing water, heavyoil sludges, cutting oils, lignin-containing waste liquors, textile oilsand other liquid targets in order to kill, prevent or inhibit the growthof microorganisms as described herein.

The formulations described herein are typically prepared by mixing theat least one non-oxidative biocide and the concentrated aqueous solutionof an inorganic halide salt, and may optionally include the mixing ofadditional ingredients, as described in detail hereinabove.

In cases where the formulations are aqueous suspension formulations,preferably, the preparation process optionally further comprises millingthe DBNP2 in the mixture.

In cases where the formulations are liquid formulations, the preparationprocess preferably include mixing and dissolving of the variouscomponents.

Additional objects, advantages, and novel features of the presentinvention will become apparent to one ordinarily skilled in the art uponexamination of the following examples, which are not intended to belimiting. Additionally, each of the various embodiments and aspects ofthe present invention as delineated hereinabove and as claimed in theclaims section below finds experimental support in the followingexamples.

EXAMPLES

Reference is now made to the following examples, which together with theabove descriptions, illustrate the invention in a non limiting fashion.

Materials and Analytical Methods

DBNPA and NaBr brine solution were obtained from ICL IndustrialProducts.

Linear alkyl benzene sulfonic acid (LABS) was obtained from ZoharDahlia.

Xanthan gum was obtained from SIGMA. Xanthan gum concentrationsindicated below are relative to the brine weight, unless otherwisespecified.

Polyethylene glycols (PEG 200 and PEG 400) were obtained from Merck(Germany).

Sodium hypochlorite (10%) was obtained from F&C LTD.

Zirconia grinding balls were obtained from IMI ceramics laboratory.

Isothiazolinon-based non-oxidant biocide LABUZID 197 was obtained fromBK Giulini.

Homogenization was performed using an Ultra-Turrax T25 (IKA Germany)dispersing system equipped with a S25-25 GM dispersing element.

The particle size was determined by laser Diffractometry.

The viscosity was measured using a Fann viscometer.

Example 1 A Homogenized Suspension of 40% DBNPA, 40% NaBr Brine and 1%Linear Alkyl Benzene Sulfonic Acid (LABS)

A NaBr aqueous solution (40% (brine), 295 grams) was mixed with a linearalkyl benzene sulfonic acid (LABS) solution (1%, 5 grams) and with2-2-dibromo 3-nitrilopropionamide (DBNPA) (200 grams) in a 500 mlbeaker. The mixture was homogenized in a dispersing system at 24,000 rpmfor 2 minutes. A triphasic “foam” (suspension with air inside) wasobtained, having a density of about 1.4 kg/liter. The mixture was storedfor one week in a 500 ml graduated cylinder. No settling of the solidwas observed and the suspension remained homogeneous.

Example 2 A Homogenized Suspension of 55% DBNPA, 40% NaBr Brine and0.55% Xanthan Gum

A NaBr aqueous solution (40% (brine), 270 grams) was mixed with xanthangum (1.5 grams) and DBNPA (330 grams) in a 500 ml beaker. The mixturewas homogenized in a dispersing system, at 10,000 rpm for 2 minutes anda suspension was obtained. The average particle size of the DBNPA in thesuspension was about 180 μm. The density of the suspension was 1.7Kg/liter. The suspension was easily poured and pumped using aperistaltic pump.

The suspension was stored for one month at ambient temperature in a 500ml graduated cylinder, and another batch was stored for one week at 50°C. The density of the upper and lower part of the suspension was in therange of 1.68-1.70 Kg/liter in both cases, indicating there was nosettling of the DBNPA.

Example 3 A Homogenized Suspension of 66% DBNPA, 40% NaBr Brine, and0.74% Xanthan Gum

A NaBr aqueous solution (40% (brine), 403 grams) was mixed with xanthangum (3 grams) and DBNPA (817 grams) in a 800 ml beaker. The mixture washomogenized in a dispersing system, with S25-25GM dispersing element at24,000 rpm for 2 minutes, to thereby obtain a suspension. The mixturewas easily poured and pumped with a peristaltic pump.

Example 4 A Solution of 20% DBNPA, PEG 400, Water and Solid NaBr

DBNPA (40 grams) was mixed with PEG 400 (64 grams, 32%) and water (72grams) at 50° C. NaBr (24 grams) was then added and the obtainedsolution was frozen and stored overnight at −15° C. After thawing, nosolid precipitates were observed in the mixture.

Example 5 A Solution of 20% DBNPA in a PEG 400 and Water Mixture

As a comparative example, a solution as described in Example 4 wasprepared, with the exclusion of NaBr.

DBNPA (40 grams) was mixed with PEG 400 (82 grams) and water (18 grams)at 50° C., and the obtained solution was frozen and stored overnight at−15° C. After thawing, solid precipitate of DBNPA appeared at the bottomof the solution.

Example 6 A Solution of 20% DBNPA in a PEG 200 and Water Mixture

As another comparative example, a solution as described in Example 5 wasprepared, using PEG 200 instead of PEG 400.

DBNPA (40 grams) was mixed with PEG 200 (96 grams) and water (64 grams)at 50° C., and the obtained solution was frozen and stored overnight at−15° C. After thawing, solid precipitate of DBNPA appeared at the bottomof the solution.

Example 7 A Homogenized Suspension of 20% DBNPA, 40% NaBr Brine and 0.6%Xanthan Gum

A NaBr aqueous solution (40% (brine), 480 grams) was mixed with xanthangum (3.0 grams) and DBNPA (120 grams) in a 1000 ml beaker. The mixturewas homogenized in a dispersing system at 10,000 rpm for 2 minutes, tothereby obtain a suspension. The mixture was easily poured from thebeaker. The suspension was stored for 10 days at ambient temperature ina 500 liter graduated cylinder with no decantation (settling) beingobserved. The suspension was easily pumped with a peristaltic pump. Themixture was stored for one week at ambient temperature with nodecantation being observed. After storage, the DBNPA concentration inthe upper and lower 70 ml portions of the suspension was 20%, indicatingno settling of the DBNPA.

Example 8 A Homogenized Suspension of 55% DBNPA, 40% NaBr Brine and 1.1%Xanthan Gum

A NaBr aqueous solution (40% (brine), 270 grams) was mixed with xanthangum (3.0 grams) and DBNPA (330 grams) in a 1000 ml beaker. The mixturewas homogenized in a dispersing system at 10,000 rpm for 2 minutes, tothereby obtain a suspension. The mixture was easily poured from thebeaker and pumped with a peristaltic pump. The suspension was stored forone week at 50° C. in a 500 liter graduated cylinder with no decantationbeing observed.

Example 9 A Homogenized Suspension of 20% DBNPA, 10% NaBr Brine and 0.6%Xanthan Gum

A NaBr aqueous solution (10% (brine), 480 grams) was mixed with xanthangum (3.0 grams) and DBNPA (120 grams) in a 1000 ml beaker. The mixturewas homogenized in a dispersing system at 10,000 rpm for 2 minutes, tothereby obtain a suspension. The mixture was easily poured from thebeaker. The suspension was stored for 10 days at ambient temperature ina 500 liter graduated cylinder with no decantation being observed. Thesuspension was easily pumped with a peristaltic pump.

Example 10 A Homogenized Milled Suspension of 55% DBNPA, 40% NaBr Brineand 0.5% Xanthan Gum

A NaBr aqueous solution (40% (brine), 540 grams) was mixed with xanthangum (2.7 grams) and DBNPA (660 grams) in a 2 liter plastic bottle of 12cm diameter filled with 2.9 kg of 6 mm diameter zirconia grinding balls.The mixture was homogenized in a dispersing system at 10,000 rpm for 2minutes, to thereby obtain a suspension. The mixture was rolled for onehour at 60 rpm, and the obtained suspension was separated from theballs. The particle size distribution was determined as d50 of 29 μm andd98 of 76 μm. A 5 ml portion of the suspension was put in an agitatedbeaker containing 1 liter of water, determining the total dissolutiontime of the particles to be 30 seconds. The mixture was easily pouredand pumped using a peristaltic pump. No settling of the solid wasobserved and the suspension remained homogeneous.

Example 11 A Milled Suspension of 55% DBNPA, Water, and 0.5% Xanthan Gum(Relative to Water)

As a comparative example, a milled suspension was prepared as describedin Example 10 above, with the exclusion of NaBr. Thus, water (540 grams)were mixed with xanthan gum (2.7 grams) and DBNPA (660 grams) in a 2liter plastic bottle of 12 cm diameter, filled with 2.9 kg of 6 mmdiameter zirconia grinding balls. The mixture was rolled for one hour at75 rpm and the obtained suspension was then separated from the balls.The particle size distribution was determined as d50 of 5.5 μm and d98of 40 μm. The suspension was viscous, difficult to pour and was notpumpable by a peristaltic pump.

Example 12 A Homogenized Milled Suspension of 20% DBNPA, 40% NaBr Brineand 0.3% Xanthan Gum

A NaBr aqueous solution (40% (brine), 480 grams) was mixed with xanthangum (1.5 grams) and DBNPA (120 grams) in a 1000 ml beaker. The mixturewas homogenized in a dispersing system at 10,000 rpm for 2 minutes, andplaced in a 1 liter plastic bottle of 12 cm diameter filled with 1.4 kgof 6 mm diameter zirconia grinding balls. The mixture was rolled for 4hours at 100 rpm, and the obtained suspension was separated from theballs. The suspension was stored for 10 days at ambient temperature in a500 L graduated cylinder and no decantation has been observed.

Example 13 A Homogenized Milled Suspension of 55% DBNPA in Water and0.5% Xanthan Gum

Water (540 grams) were mixed with a xanthan gum (2.7 grams) and DBNPA(660 grams) in a 2 liter plastic bottle of 12 cm diameter filled with2.9 kg of 6 mm diameter zirconia grinding balls. The mixture was rolledfor 1 hour at 75 rpm, and the obtained suspension was hardly separatedfrom the balls. The mixture was difficult to pour and was too viscous tobe pumped. The particle size distribution was determined to be: d50 of5.5 μm and d98 of 40 μm. These findings indicate an important role foran inorganic salt in forming a stable formulation that has desirablerheological properties.

Example 14 A Homogenized Milled Suspension of 55% DBNPA in Water and NoXanthan Gum

Water (540 grams) were mixed with DBNPA (660 grams) in a 2 liter plasticbottle of 12 cm diameter filled with 2.9 kg of 6 mm diameter zirconiagrinding bells. The mixture was rolled for 1 hour at 75 rpm, and theobtained suspension was hardly separated from the balls. The averageparticle size of the DBNPA in the suspension was of 57 μm. The mixturewas difficult to pour and was too viscous to be pumped. The particlesize distribution was determined to be: d50 of 57 pun and d98 of 148 μm.These findings further support the important role of an inorganic saltin forming a stable formulation that has desirable rheologicalproperties.

Example 15 A Homogenized Suspension of 55% DBNPA, 60% LiBr Brine and0.45% Xanthan Gum

A LiBr aqueous solution (60% (brine), 270 grams) was mixed with axanthan gum (1.5 grams) and DBNPA (330 grams) in a 500 ml beaker. Themixture was homogenized in a dispersing system at 10,000 rpm for 2minutes, to thereby obtain a suspension. The mixture was easily pouredfrom the beaker and pumped with a peristaltic pump. The suspension wasstored for one week at ambient temperature and the solids level wasdetermined to be 87% of the suspension volume. The material could beeasily pumped by a peristaltic pump. These findings show that variousinorganic halide salts can be utilized in the context of the presentembodiments.

Example 16 A Homogenized Suspension of 55% DBNPA, 40% NH₄Br Brine and0.45% Xanthan Gum

A NH₄Br aqueous solution (40% (brine), 270 grams) was mixed with axanthan gum (1.5 grams) and DBNPA (330 grams) in a 500 ml beaker. Themixture was homogenized in a dispersing system at 10,000 rpm for 2minutes, to thereby obtain a suspension. The mixture was easily pouredfrom the beaker and pumped with a peristaltic pump. The suspension wasstored for one week at ambient temperature and the solids level wasdetermined to be 97% of the suspension volume. The material could beeasily pumped by a peristaltic pump. These findings further support theindication that various inorganic halide salts can be utilized in thecontext of the present embodiments.

Example 17 Rheological Measurements of DBNPA Suspensions

The viscosity was measured for the suspensions prepared according to theprocesses described in Examples 7, 9, 10, 12, 13, 15 and 16. The resultsare presented in Table 1 below.

TABLE 1 Example % % % xanthan Shear stress (Pa) at different speeds(rpm) No. DBNPA Salt Salt gum 3 RPM 6 RPM 100 RPM 200 RPM 300 RPM 600RPM 7 20 NaBr 40 0.6 2200 1200 140 87 68 43 9 20 NaBr 10 0.6 1500 750 8756 44 29 10 55 NaBr 40 0.5 — — 275 205 180 145 (milled) 12 20 NaBr 400.3 700 350 54 38 31 22 (milled) 13 55 — 0.5 2200 1250 245 195 160 115(milled) (water) 15 55 LiBr 60 0.45 2100 1400 285 206 167 118 16 55NH₄Br 40 0.45 2400 1300 195 115 95 62

Example 18 A Solution of 20% DBNPA, PEG 400 and Water

DBNPA (40 grams) was mixed with PEG 400 (82 grams) and water (78 grams)at 50° C., and the obtained solution was frozen and stored overnight at−15° C. After thawing there was no solid deposit at the bottom of thesolution.

Example 19 A Solution of 20% DBNPA, PEG 400, Water and Solid NaBr

DBNPA (40 grams) was mixed with PEG 400 (64 grams) and water (72 grams)at 50° C. NaBr (24 grams) was then added and the obtained solution wasfrozen and stored overnight at −15° C. After thawing there was no soliddeposit al she bottom of the solution.

Example 20 A Solution of 20% DBNPA in a PEG 200 and Water

DBNPA (40 grams) was mixed with PEG 200 (96 grams) and water (64 grams)at 50° C., and the obtained solution was frozen and stored overnight at−15° C. After thawing there was no solid precipitate.

Example 21 A Solution of 20% DBNPA Using PEG 200, Water and Solid NaBr

DBNPA (40 grams) was mixed with PEG 200 (76 grams) and water (60 grams)at 50° C. NaBr (24 grams) was then added and the obtained solution wasfrozen and stored overnight at −15° C. After thawing there was no soliddeposit.

Example 22 Field Tests

A cooling tower of 1000 m³ was treated by addition of sodiumhypochlorite (10%) in a continuous mode at a rate of 60 liters per day,24 hours per day. A typical solution of an isothiazolinon-basednon-oxidant biocide was added, instead of the sodium hypochlorite, twicea week. The microbial count was of more than 10⁵ Colony Forming Units(CFU)/ml. Fouling related local corrosion was observed. Due to the highhalogen demand the free halogen content was lower than 0.1 ppm alreadyone hour after the addition of the sodium hypochlorite. The pH of thewater was in the range 8-8.5.

The addition of the isothiazolinon-based non-oxidant biocide was stoppedand sodium hypochlorite (50 liters) was added to the cooling tower at aconstant flow-rate 19 hours per day. Two hours after the sodiumhypochlorite addition was ceased the suspension prepared as described inExample 10 was added (7 kg) once every two days. The sodium hypochloriteaddition was renewed three hours later. As a result of this treatment,the bacterial count was reduced to lower than 10³ CFU/ml. After a weekof treatment, the free halogen content in the cooling water was of 0.5ppm of bromine (expressed as chlorine). No fouling-related localcorrosion was observed in the corrosion samples.

Example 23 Experiments on Simulated Biofilm Showing a Synergistic EffectExperimental Method:

The experiments were conducted based on a biofilm simulation systemdeveloped by the Biofilm Institute in Bozeman Mont. (Grobe et al., J. ofIndustrial Microbiology & Biotechnology, vol. 29 pp. 10-15), whichallows quantifying the resistance of a biofilm to biocides.

Biofilm Stimulation:

The biofilm simulation was created by entrapping bacteria in alginategel beads. A plate of R2A agar was streaked with Pseudomonas aeruginosa(ATCC 15442) and incubated at 35° C. overnight. A phosphate buffer (pH7.2) was used to scrap off the bacteria from the agar plate and create asuspension. The bacteria suspension was mixed with a 4% sodium alginatesolution at a ratio of 1:1, to obtain an alginate and bacteria slurrycontaining a 2% alginate solution.

The alginate and bacterial slurry was placed in a 50 ml syringe equippedwith a 22 gauge needle, connected to a compressed air tank, whichallowed the syringe to be pressurized. A stream of small drops of thealginate and bacterial slurry was forced out and dropped into a stirredsolution of 50 mM CaCl₂. The Ca⁺² cross-linked the alginate, andsemisolid beads with entrapped bacterial cells were formed. The beadwere stirred in the CaCl₂ solution for about 20 minutes, then rinsed ina dilute 5 mM CaCl₂ solution.

Several flasks containing 100 beads each were incubated overnight at 35°C. on a rotating shaker in a buffer solution (at desired pH), and asolution of 5 mM CaCl₂ was added to each beaker to maintain the beadsstructure. The beads diameter was about 2 mm.

Measurements of Biocidal Activity:

The buffer suspension, containing the 5 mM CaCl₂ solution, was firstdecanted and replaced by a 100 ml of the tested solution at the desiredconcentration.

A DBNPA/NaBr suspension, combining 58% DBNPA, 17% NaBr salt and 25% H₂O,was applied in combination with a sodium hypochlorite (NaOCl) solutionin two addition modes (routes): (a) addition of the sodium hypochloriteto the test system and following 15 minutes addition of the DBNPA/NaBrsuspension; and (b) addition of the DBNPA/NaBr suspension and following15 minutes addition of sodium hypochlorite. NaOCl was added in an amountcalculated so as to achieve a 1 ppm activated NaBr in the suspension.

At different time intervals, 10 beads were removed and placed in a 5grams/liter sodium thiosulfate solution containing 50 mM sodium citrate.The sodium citrate dissolves the alginate gel and releases the bacteriainto the solution.

The neutralizer-citrate solution was placed in a refrigerator for 2hours, and was thereafter diluted and plated on R2A agar plates usingpour plate technique. The plates were incubated at 35° C. for 24-48hours and than tested for bacteria counted.

The results were analyzed upon testing the neutralizer efficacy andtoxicity and were compared to the control samples.

Experimental Results

The potential synergistic effect between DBNPA, as a non-oxidativebiocide, and activated NaBr, as an oxidative biocide, was tested.

Synergism refers, as further defined hereinabove, to the phenomenon inwhich two (or more) materials acting together create an effect greaterthan that predicted by knowing only the separate effects of eachindividual material.

The results are presented in FIG. 1 and clearly show that (i) nobiocidal effect was observed in the presence of 1 ppm activated NaBr;(ii) exposure of the beads to 2.5 ppm DBNPA, resulted in 3 log reduction(as compared to control) after 30 minutes contact time. The same resultswere obtained for the activated NaBr/DBNPA suspension, added followingthe addition of the oxidative agent (route (a) hereinabove). Adding asuspension of NaBr/DBNPA and then sodium hypochlorite, via route (b)hereinabove, resulted in complete kill after 30 minutes contact time,indicating a synergistic effect between the two components.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims. All publications, patents and patentapplications mentioned in this specification are herein incorporated intheir entirety by reference into the specification, to the same extentas if each individual publication, patent or patent application wasspecifically and individually indicated to be incorporated herein byreference. In addition, citation or identification of any reference inthis application shall not be construed as an admission that suchreference is available as prior art to the present invention.

1.-53. (canceled)
 54. A method of treating an aqueous composition whichcomprises: a) introducing to an aqueous composition for which biocidaltreatment is desired a liquid formulation comprising at least onenon-oxidative biocide and a concentrated aqueous solution of aninorganic halide salt that produces an active halogen upon activation byan oxidizer; and, b) introducing to the aqueous composition an oxidizerthat activates the inorganic halide salt component of the liquidformulation to produce an active halogen in situ, the oxidizer beingintroduced to the aqueous composition prior to, with and/or followingintroduction of liquid formulation to the aqueous composition, theamount of liquid formulation and oxidizer introduced to the aqueouscomposition being effective to kill, prevent or inhibit the growth ofmicroorganisms therein.
 55. The method of claim 54 wherein thenon-oxidative biocide is at least one member selected from the groupconsisting of bronopol and 2,2-dibromo-3-nitrilopropionamide.
 56. Themethod of claim 54 wherein the oxidizer is at least one member selectedfrom the group consisting of chlorine, bromine, hypochlorite salt,hypochlorous acid, hypobromite salt, hypobromous acid, a halogenatedhydantoin, a halogenated isocyanurate, a peroxide and a persulfate. 57.The method of claim 54 wherein the liquid formulation further comprisesa solvent.
 58. The method of claim 57 wherein the organic solvent is aglycol.
 59. The method of claim 58 wherein the glycol is a polyalkyleneglycol.
 60. The method of claim 59 wherein the polyalkylene glycol is apolyethylene glycol.
 61. The method of claim 54 wherein the aqueouscomposition for which biocidal treatment is desired is at least onemember selected from the group consisting of drinking water, sewagewater, process water used in papermaking, process water used inindustrial cooling, washing water, heavy oil sludge, cutting oil,lignin-containing liquor and textile oil.
 62. The method of claim 61wherein the non-oxidative biocide is at least one member selected fromthe group consisting of bronopol and 2,2-dibromo-3-nitrilopropionamide.63. The method of claim 61 wherein the oxidizer is at least one memberselected from the group consisting of chlorine, bromine, hypochloritesalt, hypochlorous acid, hypobromite salt, hypobromous acid, ahalogenated hydantoin, a halogenated isocyanurate, a peroxide and apersulfate.
 64. The method of claim 61 wherein the liquid formulationfurther comprises a solvent.
 65. The method of claim 64 wherein theorganic solvent is a glycol.
 66. The method of claim 65 wherein theglycol is a polyalkylene glycol.
 67. The method of claim 66 wherein thepolyalkylene glycol is a polyethylene glycol.
 68. The method of claim 61wherein the inorganic halide salt is sodium bromide and the oxidizer isat least one member selected from the group consisting of hypochloritesalt and hypochlorous acid.
 69. The method of claim 68 wherein thenon-oxidative biocide is at least one member selected from the groupconsisting of bronopol and 2,2-dibromo-3-nitrilopropionamide.
 70. Amethod of treating an aqueous composition which comprises: a)introducing to at least one aqueous composition selected from the groupconsisting of drinking water, sewage water, process water used inpapermaking, process water used in industrial cooling, washing water,heavy oil sludge, cutting oil, lignin-containing liquor and textile oilfor which biocidal treatment is desired a liquid formulation comprisingat least one non-oxidative biocide selected from the group consisting ofbronopol and 2,2-dibromo-3-nitrilopropionamide, and a concentratedaqueous solution of sodium bromide; and, b) introducing to the aqueouscomposition at least one oxidizer selected from the group consisting ofhypochlorite salt and hypochlorous acid, the oxidizer activating thesodium bromide to produce an active bromide in situ, the oxidizer beingintroduced to the aqueous composition prior to, with and/or followingintroduction of liquid formulation to the aqueous composition, theamount of liquid formulation and oxidizer introduced to the aqueouscomposition being effective to kill, prevent or inhibit the growth ofmicroorganisms therein.
 71. The method of claim 70 wherein the liquidformulation further comprises a solvent.
 72. The method of claim 71wherein the solvent is a polyalkylene glycol.
 73. The method of claim 72wherein the polyalkylene glycol is a polyethylene glycol.